"The Bar Association is concerned that some aspects of the Premier's statements, to the effect that police and ambulance officers should have the support of the court system, could undermine public confidence in the court system itself," he said.

"There should be no special categories of witnesses or occupations marked out for special treatment in the court system."

The letter to Mr O'Farrell from association president Bernard Coles QC says the Premier's statements do not accurately reflect the roles of the courts.

Mr O'Farrell has rejected the criticism, saying even the state's Supreme Court has criticised some of Ms O'Shane's decisions.

He says it is the way Ms O'Shane has treated evidence that has undermined public confidence.

"I'm not going to back away from my strong position of defending police, ambulance officers, fire and rescue officers as they go about their work," Mr O'Farrell said.

"The job of the Premier is to ensure the public get the message that when asked to do something or asked to cooperate with those people, they should do so."